Brake retractor mechanism

ABSTRACT

A brake retractor assembly in which the automatic adjustment mechanism includes a locking plate assembly for gripping the retractor rod in a tilted position and a friction engaging member carried by the locking plate for relative rotational movement therewith so that the friction engaging face of this member conforms to the face of the retractor rod.

United States atent C. Lucas Plant;

Arthur J. Thrower, both of Troy, Ohio 855,498

Sept. 5, 1969 June 29. 1971 The B.F. Goodrich Company New York, N.Y.

Inventors Appl. No. Filed Patented Assignee BRAKE RETRACTOR MECHANISM 4Claims, 4 Drawing Figs.

US. Cl ran/11%, l88/7l.8 Int. Cl ..lFl6d 65/54, Fl6d 55/18 Field ofSearch 188/7113,

[56] References Cited 7 UNITED STATES PATENTS 2,889,104 5/1959 Prayer188/71 .8 2,951,560 9/1960 Smellie l88/7l.8 3,091,310 5/1963 Smith et al188/196 Primary Examiner-Duane A. Reger Attorneys-John D. Haney andHarold S. Meyer ABSTRACT: A brake retractor assembly in which theautomatic adjustment mechanism includes a locking plate assembly forgripping the retractor rod in a tilted position and a friction engagingmember carried by the locking plate for relative rotational movementtherewith so that the friction engaging face of this member conforms tothe face of the retractor rod.

PATENTEDaunzeusm 3.589479 sum 2 OF 2 -\27 22 2/ 1 3/1 3 i /2es 3Q" 19 3333 l7 1 F|G.2.

INVENTORS C. LUCAS PLANT ARTHUR J. THROWER BRAKE IRETRACTOIR MECHANISMBACKGROUND OF THE INVENTION This invention relates to mechanism forautomatically maintaining a uniform release clearance (and therefore auniform actuating stroke) for brakes and similar equipment. Mechanismsof this type are commonly used in brake systems to compensate for wearof the brake linings and other brake parts and are popularly calledautomatic brake adjusters." Although the present invention is explainedhere in connection with brakes, the mechanism has utility in otherenvironments where similar wear compensation is needed such as inclutches.

For many years, brake adjusters or wear compensators have been of twobasic designs. The mechanical adjusters utilized special ratchets orfriction-dragging parts to control the adjustment and the hydraulicadjusters utilized the metering of hydraulic fluid to provideadjustment. A sophisticated form of hydraulic adjuster is described, forexample, in U.S. Pat. No. 2,926,498 and a mechanical ratchet adjuster isdescribed, for example, in U.S. Pat. No. 1,825,555. An improved form ofmechanical adjuster in which the step-by-step adjustments of theratchet-type adjuster are avoided and the adjustments can be made insmall increments is shown and described in U.S. Pat. No. 2,392,970 andUS. Pat. No. 3,091,310 in which gripping of the retractor rod isprovided through the use of collets or locking plates.

In the design of new aircraft the capacity of the brakes has beenincreased; however, the space for the brake elements has not beenincreased. Accordingly, the need is for a brake retractor mechanismwhich will provide more clamping force in the same package. It is alsoessential that the clamping force be substantially constant so that acontrollable adjustment for brake wear is obtained to provide a constantrelease clearance.

Another requirement for brake retractors is that the clamping forceremain high and the operation remain predictable even after substantialwear takes place. Still another requirement is that an improved lockingplate assembly be adaptable for use in retractors which have the samedesign as that used for older type locking plates. The aboverequirements must be provided in an assembly which is relativelyservice-free and is substantially free of assembly and installationproblems SUMMARY OF THE INVENTION The locking plate assembly of thisinvention includes a clamping member which may be substituted forlocking plates of the type found in other brake retractors but whichprovides substantially more clamping force on the retractor rod. The useof a tiltcompensating cam carried by the clamping member increases theclamping force which is exerted against a substantially flat surface onthe retractor rod.

The clamping member has an opening through which the retractor rod isdisposed and in the preferred construction the retractor rod has asquare cross section so that the surfaces which are engaged by theclamping member are substantially flat. Interposed between one edge ofthe opening and the face of the retractor rod is a cam ortilt-compensating member which is connected to the clamping member by apivot pin. The cam pivots around an axis which is substantiallyperpendicular to the plane in which the clamping member tilts. As theclamping member tilts in one direction the cam is urged into frictionalengagement with the flat surface of the retractor rod because thedistance between the pivot pin and the edge of the opening in theclamping member is foreshortened. The face of the cam which engages theretractor rod has contact points which are spaced apart in thelongitudinal direction of the retractor rod so that the engaging facesof the cam and rod will conform. In this manner the cam compensates forthe tilt of the clamping member and even though there is wear of thepivot pin and clamping member, the clamping force remains substantiallyconstant. The clamping force is also distributed over a wider area ofthe retractor rod than is possible with the type locking clamp usedheretofore.

When the clamping member is tilted in the other direction the distancebetween the axis of the pivot pin and the edge of the opening in theclamping member is increased permitting slippage of the retractor rodthrough the clamping member. This relative movement of the clampingmember and rod is necessary to compensate for the wear between the brakediscs. After this compensating movement has taken place the retractorspring will operate against the end of the clamping member to providetilting action which will again result in substantial clamping forcebeing exerted against the retractor rod for locking the clamping memberand the retractor rod together.

The accompanying drawings show one preferred form of brake retractormade in accordance with an embodying this invention and which isrepresentative of how this invention may be practiced.

BRIEF DESCRIPTION OF THE DRAWING In the drawings:

FIG. l is a longitudinal cross section of the retractor assemblyinstalled in a typical disc brake, the assembly being in the conditionits parts occupy when the brake is retracted or released, the brakeparts being shown in generalized or somewhat schematic form with someparts being broken away.

FIG. 2 is a view corresponding to FIG. 1 except that the brake isengaged and the retractor assembly is in the condition its parts occupyduring an adjusting movement of the locking plate assembly to compensatefor wear of the brake friction faces;

FIG. 3 is a view on the line 3-3 of FIG. ll; and,

FIG. 4. is a view in section taken along the line 4-4 of FIG. I.

DETAILED DESCRIPTION A retractor assembly 10 is mounted rigidly in atorque frame ll. of a brake, the frame in turn being adapted formounting to a vehicle structure (not shown). The frame 111 carries alining carrier 12 in parallel axial alignment with a rotatable disc I3.The latter is in splined engagement at its periphery with a rotarymember 14 which may be part of the wheel structure with which the brakeis associated. On the other side of the rotatable disc 13, in the areawhich is broken away, another lining carrier and retractor assembly likethat shown may be mounted on the torque frame 11.

The brake is actuated and the brake members engaged by a hydraulicpiston 15 mounted in a cylinder I6 in the brake frame Ill. In responseto hydraulic pressure the hydraulic piston I5 urges the lining carrier112 against the brake disc 13 which resists axial movement by engagingother brake members (not shown). The brake members as shown in FIG. Iare in the released condition with the lining carrier 12 and therotatable disc 13 out of engagement. In FIG. 2 the retractor assembly isshown in the actuated condition with the brake members in engagement.

The brake retractor assembly 10 includes a cylindrical housing 17 whichmay be part of the brake frame ill or adapted for tight anchorage insidethe brake frame as shown in FIG. l.

A retractor rod 118 extends through the housing 17 and towards thebraking members where it is connected to the lining carrier 12 as byinsertion of an enlarged head 19 of the retractor rod in a slot 21 ofthe lining carrier as shown in FIG. I or by other arrangements wellknown in the art.

The cylindrical housing 17 has an annular flange 22 at the end adjacentthe braking members which supports the retractor rod 1% forreciprocation therein. A cylindrical potion 23 of the retractor rod 118is in slidable engagement with the annular flange 22.. The portion ofthe retractor rod 13 at the opposite end is supported concentrically ofthe housing 17 by an annular cover plate 24 fastened securely in theouter open end of the housing by a snap ring 25. At this end of theretractor rod 18 the portion projecting through the cover plate 24 has asubstantially square cross section as shown in FIGS. 3 and 4 andtherefore the center hole in the plate 24 is also of a squareconfiguration with a sliding clearance between the edges of the hole andthe rod to permit free reciprocation.

A helical-coiled retractor spring 26 is housed inside the housing 17concentrically surrounding the rod 18 and annular flange 22. Theretractor spring 26 is caged under compression in the housing 17 withthe right end coil of the spring (as viewed in FIG, 1) bearing againstthe inner end wall of the housing 17 and the left end coil bearingagainst a flanged collar 27 which is slidable loosely on the portion ofthe retractor rod 18 having the square cross section. The helical spring26 biases the collar 27 leftward into engagement with a locking plateassembly 28 which has a clamping member 29 surrounding the rod 18 in theregion between the flanged collar 27 and the end cover plate 24.

The clamping member 29 is a generally annular disc and includes acentral opening 31 through which the rod 18 projects. Lower edge 32 ofthe opening 31 is disposed in close sliding proximity to a lower flatface 33 at the underside of the retractor rod 18 and preferably has twoflat faces 34 and 35 which come together at a pivoting edge 36.

The opening 31 has an upper edge 37 which is spaced from the upper face38 of the rod 18 providing a slot 39 in which a frictional-engagingtilt-compensating member such as cam 41 is mounted for turning movementabout a pivot pin 42 connected to the clamping member 29. The pivot pin42 has an axis which is preferably perpendicular to a vertical planepassing longitudinally through the center of the housing 17 andretractor assembly 10.

As shown in FIGS. 1 and 4 the cam 41 has a rod-engaging face 43 withcontact edges 44 and 45 which are apaced apart for contacting the rod atlongitudinally spaced-apart positions. These contact edges arepreferably straight for engaging the flat upper face 38 of the rod 18.

Opposing radial faces 46 and 47 of the clamping member 29 taper towardseach other from a thick region 48 to a thinner region 49 at the loweredge of the clamping member. The biasing force of spring 26 urges collar27 against the thin region 49 of the clamping member 29, thereby tiltingor canting this member so that the pivoting edge 36 at the lower edge ofthe opening and the contact edges 44 and 45 on the face of the cam 41engage the rod 18 and provide sufficient clamping force to preventslippage of the retractor rod through the locking plate assembly 28.

In the released condition of the brake as shown in FIG. 1, the flangedcollar 27 under the bias of spring 26 presses the thick region 48 of theclamping member tightly against the end cover plate 24 to provide apositive retracted position for therod 18. The flanged collar 27actually bears against the clamping member 29 only at the projectingedge of the thinner region 49. Along the opposite face of the thickregion 48 clamping member 29 is beveled at 51 so that the opposite sideof the clamping member engages cover plate 24 at an edge of bevel 51which is radially offset inwardly from the periphery of clamping member29. This arrangement insures that the clamping member 29 remains tiltedand in engagement with the rod 18 when the rod is in a retractedposition as in FIG. 1 and it may be noted that in this retractedposition the opposing faces 46 and 47 of the clamping member slant awayfrom their respective adjoining surfaces on cover plate 24 and collar27.

The upper peripheral edge 52 of the clamping member 29 includes a lobeor projection 53 which extends into a slot 54 in the housing wall. Thisslot 54 terminates in a shoulder 55 which is of greater diameter thanthe flanged collar 27 so that the collar cam slide past the shoulderwhen the rod 18 is reciprocated. The shoulder 55 is adapted to engagethe projection 53 of the clamping member 29, however, whenever the rodis advanced rightward for a distance sufficient to bring the projection53 against this shoulder.

When the brake is operated by communicating hydraulic fluid to piston 15the latter displaces lining carrier 12 rightward pulling rod 18 axiallythrough the flange 22 of housing 17. Clamping member 29 moves rightwardas the rod 18 advances because the biasing force of spring 26 againstflanged collar 27 maintains the clamping member tilted in tightfrictional engagement with the rod 18. Tilting of the clamping member 29causes a clamping force to be exerted between the pivoting edge 36 ofthe opening 31 and the rod engaging face 43 of the cam 41. Regardless ofthe tilting of the clamping member or the wear of the parts the cam 41transmits the torque from the pivot pin 42 to the contact edges 44 and45 where the clamping force is evenly distributed and the turning actionof the cam 41, therefore, compensates for the tilting of the clampingmember 29.

Should there be no appreciable wear or other conditions materiallychanging the release clearance between the lining carrier 12, rotatabledisc 13 and other braking members while these members are engaged, thenrod 18 will not be axially displaced an amount sufficient to bringprojection 53 of the clamping member 29 against the shoulder 55. Insteadthe locking plate assembly 28 will remain engaged with the rod 18 andwhen the brake actuation pressure is released the retractor spring 26will expand to displace the rod to its original starting position.

The retractor assembly 10 is designed so that the distance designated bydimension "X" in FIG. 1 between the annular shoulder 55 and the releasedposition of the projection 53 is equal to the maximum allowable releaseclearance between the lining carrier 12 and the adjoining brakingmembers. So long as the release clearance does not exceed an amountindicated by dimension X" the locking plate assembly 28 will alwaysremain in tight frictional engagement with rod 18 and the brake membersmay be engaged and released repeatedly.

Owing to the erosion of the brake lining as the brake is used, therelease clearance between the retracted position of the lining carrier12 and the adjoining brake members tends to increase progressively. Theexistence of this condition is automatieally sensed in this mechanismbecause rod 18 and lining carrier 12 can be displaced for whateverdistance necessary to bring about brake engagement regardless of wear.Accordingly, whenever the lining carrier 12 and rod 18 are moved througha distance greater than that equal to dimension X" in order to engagethe rotatable disc 13 and other braking members, the projection 53 ofthe clamping member 29 will be forced into engagement with shoulder 55.The latter then urges the clamping member 29 into its position shown inFIG. 2 in which the frictional engagement of the cam 41 with rod 18 isreleased. Rod 18 can then be slid forward freely through the opening 31in the clamping member 29 for whatever distance is required to maintainbrake engagement. On the subsequent release of fluid pressure againstthe piston 15 the retraction forces on the brake members will act tomove rod 18 in the reverse direction and the biasing force of theretractor spring 26 against collar 27 is immediately effective to tiltthe clamping member 29 into its frictionally engaged position urging cam41 and the rod engaging face 43 into frictional engagement with rod 18.Accordingly, the retractor spring 26 will then through the agency of thereengaged clamping member 29 retract the lining carrier 12 from theother brake members. Since the retraction stroke is limited by thedistance clamping member 29 can move before it abuts cover plate 24, therod 18 is retracted only a distance equivalent to dimension X" andtherefore a new starting position is established for the rod and thelining carrier 12 in which the release clearance between the liningcarrier, the rotatable disc 13 and the other brake members is againequal to dimension X.

The progressive relocation of the starting position of the rod 18 andthe lining carrier 12 in this manner does not change the maximumdeflection amplitude of the retractor spring 26. The retractor springdeflection amplitude remains substantially the same on every actuationfrom the time the brake is new until the lining is entirely worn out.

In high energy brakes where the hydraulic. pressure used to actuatepiston and cylinder 16 is necessarily high, There may be back pressurein the cylinder tending to urge the rod 18 rightward in FIG. 1 when thebrake is released. It is, there fore, desirable that the clamping forcebe adequate to prevent slippage of the locking plate assembly 28 alongthe rod 18. In

this invention the clamping force exerted by the rod engaging face 43 ofcam 41 against the rod 18 insures that the rod will remain in anyadjusted position. Also, if there is wear of the pivot pin 42, rodengaging face 43, pivoting edge 36 or lower face 33 and upper face 38'ofthe rod, this will be compensated for by the rotation of cam 41 on thepivot pin 42 and the same substantial clamping force will be exertedagainst the rod 18.

To reline the brake, the position of the rod 18 may be reset by pushingthe lining carrier 12 toward the housing 17. When such force is appliedaxially of rod 18, the clamping member 29 turns against the spring 26 toa position in which the locking plate assembly 28 is released fromfrictional engagement with the rod 18 and the rod can be slid leftwardto its original position.

Depending on the size of the brake, one or a number of these retractorassemblies may be used in arcuately spaced positions in the torqueframe.

We claim:

1. A locking plate assembly for a brake retract'or mechanism comprisinga rigid clamping member having an edges having a tilt-compensatingmember mounted thereon for turning movement relative to said clampingmember, said compensating member having a surface for frictionalclamping engagement with said rod and said surface contacting said rodat spaced-apart positions to provide a turning movement of saidcompensating member until there is conformance of said surface with theface of said rod as said pair of opposing edges are urged together upontilting of said clamping member.

2. A locking plate assembly according to claim 1 wherein saidcompensating member is mounted for relative turning movement about anaxis perpendicular to the plane in which said clamping member tilts.

3. A locking plate assembly according to claim 2 wherein saidcompensating member is connected to said clamping member by a pivot pindisposed along said axis.

4. A locking plate assembly according to claim 1 wherein said surfacefor frictional clamping engagement with said rod has straight edgeswhich engage a flat face of said rod to provide maximum clamping forces.

Patent NO- D d June 29,

n fls) C. Lucas Pleat and Arthur J. Thrower It is certified that errorappears in the above-identified patent and that said Letters Patent arehereby corrected as shown below:

I! Column 3, line 36 "apaced" should read ---spaced---.

Column 3, line 71, "cam" should read --can--.

Column 5, line 2, "There" should read ---there---.

In the references cited, "2,889,104" should read ---2,888,l0

Signed and sealed this 25th day of January 1972.

firtitest:

-- T ROBERT GOTTSCHALK c nk- 1) M.FLETCHER, JR. of Patents Q omaztirggOfficer Commlssloner

1. A locking plate assembly for a brake retractor mechanism comprising arigid clamping member having an opening through which a retractor rod isdisposed, means to tilt said clamping member relative to said rod tobring a pair of opposing edges of said opening into clamping engagementwith the face of said rod, at least one of said pair of opposing edgeshaving a tiltcompensating member mounted thereon for turning movementrelative to said clamping member, said compensating member having asurface for frictional clamping engagement with said rod and saidsurface contacting said rod at spaced-apart positions to provide aturning movement of said compensating member until there is conformanceof said surface with the face of said rod as said pair of opposing edgesare urged together upon tilting of said clamping member.
 2. A lockingplate assembly according to claim 1 wherein said compensating member ismounted for relative turning movement about an axis perpendicular to theplane in which said clamping member tilts.
 3. A locking plate assemblyaccording to claim 2 wherein said compensating member is connected tosaid clamping member by a pivot pin disposed along said axis.
 4. Alocking plate assembly according to claim 1 wherein said surface forfrictional clamping engagement with said rod has straight edges whichengage a flat face of said rod to provide maximum clamping forces.